Feeds

back to article Raygun 747 missile-zapping test video released

The US Missile Defence Agency has released video of last week's test of the Airborne Laser Testbed (ALTB) - the huge, jumbo-jet-mounted laser cannon built to blast hostile ballistic missiles out of the sky as they boost upward from their launch sites. The ALTB was formerly known simply as the Airborne Laser (ABL), but has had …

COMMENTS

This topic is closed for new posts.
Silver badge
Joke

It would be a hell of a way

to light a barbeque

2
0
Boffin

Counter measures ?

Now while I haven't tried this, I'm wondering if wrapping missiles in a special reflective materiel (that's up to the job) wouldn't render the laser canon ineffective?

0
0
Boffin

Re: Counter measures ?

Wrapping it in tipfoil might make it look pretty, but it's not likely to do much for heat dissipation.

0
0
Bronze badge
Boffin

The title is required, and must contain letters and/or digits.

Apparently not - unless it's 100% reflective, some of it will be vaporised and the vapour will start to absorb the laser energy instead, then the energy just conducts as heat into the coating (which then disintegrates).

Or so I read.

0
0
Silver badge
Boffin

One might still

coat a missile with an ablation-type heat shield (think Apollo era). If it is also reflective (in the correct wavelength band) it will reflect part of the heat, but that by itself is apparently not enough. However, if you allow a thick shield to evaporate this has two effects: It carries the heat away from the missile effectively, and could create a cloud of droplets or particles which could scatter part of the laser energy. The vapour absorbing energy is not a problem as it will not conduct energy to the missile effectively.

Launching missiles in thick fog could help, but IR travels quite far through fog (would reduce range further though).

1
0
Black Helicopters

Events are accurate but not shown in realtime

so err how long were they frying it for.. couple of hours/days??

1
0

lasers - my arse

WTF??? Nothing here that couldnt be run off in 10 mins with a cracked copy of After Effects.....

1
0
WTF?

Hey Wait

What ever happened to the ground based one we were supposed to sell to Israel? The one that was shooting tank shells out of the sky?

1
0

It was completed and successfully tested

However there were strong objections to the disposal of the toxic waste produced. Apparently the residents of the northern towns actually felt it was safer to put up with the occasional missile (most land harmlessly) than have a large toxic waste dump near by - though this was before the big increase prior to the last major Israeli incursion of Gaza.

0
0
Megaphone

Well

Just slap a nuclear reactor in the back of the plane. Electro lasers powered by such would be more than capable of one-shotting a missile in a few seconds, not this horrid 1-minute crap. Hate to have to stem off 5 missiles at once.

1
0
Gold badge

@Ammaross Danan

First off, "slapping a nuclear reactor in the back of a plane" would violate quite a few treaties, not to mention make eleventeen squillion NIMBYs explode.

Secondly, you could put the biggest power source you wanted on that plane, but power generation isn't the problem. (Power generation on something the size of a 747 isn’t a problem. The solid state array required for a megawatt-class laser isn’t that big, leaving plenty of room for old-fashioned fossil-fuel-based generators.)

Heat is the killer to this idea. A large portion of all the energy you are pumping out is converted to light, but not all...when you are talking megawatt class lasing, this is a terrific engineering problem. You have to sink that heat off your lasers, (and possibly your focusing mechanisms, I honestly don’t know the answer to that one,) conduct that heat to an appropriate radiator, and then radiate it away.

Big ass water-cooling system and/or heat pipes can help with some of that, but where do you dump the heat? Directly into the atmosphere isn't exactly an option. The air be a little thin where they be lasing, and the surface area required starts to boggle the mind. I am sure with enough time and effort the heat dissipation issue can be overcome, perhaps by recycling the waste heat into sub-generation, perhaps by using heat pumps to dump the heat as super-heated exhaust. This gets into the realm now of muchos big time maths, and a lot of trial-and-error.

Either way, we can cheerfully pack a megawatt+ worth of generation capacity onto a 747 without ever having to put fissionables into a position where they might be blown up in our atmosphere. Avoiding the scattering of fissionables everywhere helps keep the rate of exotic cancers down.

If you can come up with some neat ways to overcome the heat dissipation problems however, then DARPA would love to hear from you.

1
0
Silver badge

Actually, quite a large percentage is heat

Some 50% or more. Getting rid of heat is one of the real thermodynamical nightmares. As Eddington (I think it was) once said: "If you want to break the second law of thermodynamics, there is no hope."

0
0
Black Helicopters

.. dejavu?

I feel I've read this article somewhere else before.......

Questionable time stamps on the video, as I have seen the second segment at the end of last year...

Blackhelicopters, as something is turning rank very quickly...

0
0
Boffin

What was that?

There were some pictures of coloured lights. I have no idea what they meant. There's certainly nothing to confirm that it was a raygun blootering a rocket out of the sky.

0
0
Coat

Fake!

Obviously fake.

Everyone knows that lasers go PEW!PEW! when fired.

3
0
Silver badge

This is geniune?

Nothing I couldn't do with a cheap laser pointer, halogen-bulb torch, couple of christmas tree lights, and a low-band video camera running with the focus wonky. Don't even need computer editing beyond VirtualDub for splicing the bits together...

0
0
Silver badge

"[the Iranian missile threat] did not come as fast as we thought it’d come"

Somewhat like the WMD menace in Iraq then, eh ?

Good thing they didn't invade first, this time.

1
0
Alert

Quite a few defense analysts..

..over the last few years have clutched their crystal balls and opined that when it all kicks off, Israel will be involved.

They're mighty jumpy over there, a bunch of warlike right wingers running the military of a nuclear state- surrounded by countries which really are out to get them, paranoia aside. Hell of a situation- my money is on Israel nuking Iran or vice versa. It's not going to be good.

On the upside, if things get out of hand, living in London, I'll be a prime nuke target, and likely die nice and fast :)

1
0
Gold badge
Happy

running some numbers

Heat could well be the long pole in this tent. The laser diode pumped lasers are pretty good on this at (IIRC) about 32% efficiency. I've no idea what chemical systems are. From memory HeNe is around 5%. The rest (68% or 95% depending on system) is heat. Chemcial systems were chosend for their (apparent) mechancial simplicity, not necessarily for there efficiency.

So a MW class laser has to dump somewhere between 2 and 19MW. To put that in perspective. 1MW/m^2 was the Apollo heat shield spec (which at 100W/cm^2 is also roughly the heat output of a modern CPU).

So you're looking at 2-19 square metres (205 Sq Ft) of heat dumping surface. Large but not impossible *provided* you have a heat sink to dump the heat into. It would not be the first time people have used the fuel for cooling. Likewise engine intake air (at 40kft) is also pretty cold If the efficency is <5% then you're proportionately in bigger trouble. Heat pipe cooled leading edges were proposed for the space shuttle (the top surface of the wing during re-entry is a *lot* cooled than the edge or windward sides) but an aircraft with a wing mounted radiator has not (AFAIK) flow since the 1930's.

0
0
Pirate

Real Genius

Val Kilmer will be so pissed

1
0
This topic is closed for new posts.